JP2000022192A - Snow detector for solar cell and automatic snow melting system employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a snow detector for solar cell in which solar energy can be utilized to the maximum by melting snow before sunrise. SOLUTION: A stroboscope 2 for for irradiating the light receiving face of a solar cell 5 is provided and a voltage generated from the solar cell 5 upon irradiation is detected by a voltage detecting means 4. A snow decision circuit 21 compares the voltage with a specified level and makes a decision that snow is not deposited if the former is higher and then delivers a detection signal 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the accumulation of snow on the surface of a solar cell and an apparatus for automatically melting the snow.

[0002]

2. Description of the Related Art There is a so-called solar power generation system in which sunlight is received by a solar cell (photoelectric converter) and power is generated. Since solar cells in solar power generation systems are often installed outdoors, snow accumulates on the battery surface during snowfall, which blocks light and hinders power generation.Therefore, it is first detected by some method that there is snow on the surface. If snow is detected, it is necessary to remove the snow in some way.

FIG. 7 is a diagram showing voltage / current characteristics of a solar cell. At the time of power generation, the solar cell operates according to the characteristic of the characteristic line A in which both the voltage and the current are positive, and the operating point is determined by the load on this characteristic line. On the other hand, dark state (when no power is generated)
When a voltage is applied from the outside, current flows in the direction opposite to that at the time of power generation, and operates as a characteristic shown by a characteristic line B in FIG. That is, it has a snow melting function.

FIG. 8 is a block diagram of a photovoltaic power generation system having a snow melting function similar to that shown in Japanese Patent Application Laid-Open No. 9-23019, for example. It is a thing using. In the figure,
Reference numeral 5 denotes a solar cell, 6 denotes a backflow prevention diode, 7 denotes a power generation / snow melting mode switch, 8 denotes an inverter, and 9 denotes a power system. Solar cell 5 during the day and without snow
When power is being generated, the power generation / snow melting mode switch 7 (also simply referred to as a switch) is turned off (the state shown in FIG. 8).
The DC power generated by the solar cell 5 is converted into AC power by the inverter 8 through the backflow prevention diode 6 and transmitted to the power system 9.

Reference numeral 20 denotes an infrared snowfall sensor. When the infrared snow sensor 20 detects snowfall, or when a person recognizes snow on the surface of the solar cell 5, the power generation / snow melting mode switch 7 is turned on and the inverter 8 is operated in the charging mode (converter mode). I do. And power system 9
Power is supplied through the route from the inverter 8 to the switch 7 to the solar cell 5, and the solar cell 5 is operated with the characteristics shown in FIG. 7B to generate heat and melt snow. The person confirms that the melting of the snow has ended, and returns the power generation / snow melting switch 7 to the original position. Here, instead of the power system 9 and the inverter 8, a battery or a DC power supply (both not shown) may be connected to energize the solar cell 5. An example using a battery is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-254.
635.

[0006] Such a snow melting method for generating heat from the solar cell 5 itself uses the solar cell 5 as a heater, and thus operates when there is no snow, or does not return the switch 7 to the original state after the snow has been completed. Otherwise, power is wasted. Instead of the infrared snowfall sensor 20, a rainfall sensor (not shown) is also used. There is also a method of detecting the presence or absence of snow using the open voltage at the time of power generation of the solar cell.

[0007]

The conventional snow detector for a solar cell is constructed as described above, but has the following problems. 1. Infrared-type snowfall sensors and rainwater sensors do not directly detect snowfall, even if they can detect snowfall. Completion cannot be detected. 2. Since the method of detecting the presence or absence of snow by the open voltage of the solar cell can be used only in the daytime with solar radiation, if it was detected and then melting snow,
There is a problem that the opportunity of power generation by morning sunlight is missed, and when snow melting is completed during the night, it cannot be used for detecting the completion of snow melting.

The present invention has been made to solve the above-mentioned problems. 1) It is possible to directly detect snow cover on the light receiving surface of a solar cell, 2) It is possible to operate even at night without solar radiation, 3) After melting the snow, the completion of the snow melting can be detected even at night. Accordingly, an object of the present invention is to provide a snow detector for a solar cell that can melt snow before sunrise and utilize solar energy to the maximum.

[0009]

According to the present invention, there is provided a solar cell snow detecting apparatus having a light receiving surface for receiving sunlight, a strobe light emitting device provided to irradiate the light receiving surface, A switch circuit for operating the strobe light emitting device, voltage detecting means for detecting the output voltage of the solar cell, and comparing the output voltage of the solar cell detected by the voltage detecting means when the strobe light emitting device emits light with a predetermined value. And determining whether there is snow on the light receiving surface of the solar cell and transmitting a snow detection signal. The strobe light emitting device and the voltage detecting means can confirm the magnitude of the power generation capacity of the solar cell, that is, the presence or absence of snow, regardless of time or weather.

[0010] The snow-snow judging circuit of the snow-snow detector for a solar cell according to the present invention has a predetermined time T immediately after the operation of the switch circuit.
During s, the output voltage of the solar cell is compared with a predetermined value.

In the apparatus for detecting snowfall of a solar cell according to the present invention, the switch circuit is operated at an arbitrary cycle while the output voltage of the solar cell when the switch circuit is not operated is equal to or lower than a predetermined value. It has a snow detection command circuit.

The present invention further has a snow detection command circuit for operating the switch circuit at a predetermined time.

Further, the apparatus has a temperature detection circuit for detecting a temperature in the vicinity of the solar cell and transmitting a snow detection instruction prohibition signal to the snow detection command circuit when the detected temperature is higher than a predetermined value.

Further, the strobe light emitting device has a storage box having a glass window for storing the strobe, a heater for heating the glass of the glass window, and a heater opening / closing circuit for turning on / off the power of the heater. .

The solar cell snow detector according to the present invention is a solar cell array in which some of the solar cells include a plurality of solar cells each having one strobe light emitting device. The array has one voltage detecting means, one snow determining circuit, and a timer circuit for sequentially operating the strobe light emitting device.

Further, the predetermined time Ts is 5 ms to 10 ms.
00 ms.

An automatic snow melting apparatus for a solar cell according to the present invention includes a solar cell having a light receiving surface for receiving sunlight, a strobe light emitting device provided to irradiate the light receiving surface with radiation, and operating the strobe light emitting device. A switch circuit, a voltage detecting means for detecting an output voltage of the solar cell, and comparing the output voltage of the solar cell detected by the voltage detecting means at the time of light emission of the strobe light emitting device with a predetermined value, for detecting the output voltage of the solar cell. A snow detection device having a snow determination circuit for determining the presence or absence of snow on the light receiving surface and transmitting a signal corresponding to the presence or absence of snow, and a power supply device for outputting a voltage; It has a snow melting circuit for applying the voltage of the device to the solar cell for a certain period of time.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a snow cover detecting device for a solar cell according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a snow detector for a solar cell according to the present invention. In the figure, 1 is a snow detection unit, 21
Is a snow accumulation determination circuit, 3 is a switch circuit, and 31 is a snow accumulation detection signal. During the daytime and when the solar cell 5 is generating power without snow, the DC power generated by the solar cell 5 is converted into AC power by the inverter 8 through the backflow prevention diode 6 and transmitted to the power system 9. You. Reference numeral 2 denotes a strobe light emitting device provided to irradiate the light receiving surface of the solar cell 5 with light. 3 denotes a switch circuit for causing the strobe light emitting device 2 to emit light. 4 denotes a voltage divider for detecting the voltage of the solar cell 5 (voltage detecting means). ). Reference numeral 21 denotes a snow determination circuit that compares the voltage of the voltage divider 4 with a predetermined voltage and outputs a snow detection signal 31 based on the result. In addition, the switch circuit 3 and the snow determination circuit 21 constitute the snow detection unit 1.

Although the light of the strobe light emitting device 2 is not as intense as sunlight, when the solar cell 5 is irradiated at night when there is no sunlight, as shown in the experimental example shown in FIG.
A voltage having a peak at 0% is generated for several tens of ms. However, when snow is present on the light receiving surface of the solar cell 5, the light of the strobe light emitting device 2 is blocked, and no voltage is generated.
The light receiving of the solar cell 5 is performed by comparing the output voltage of the voltage divider 4 with a voltage slightly lower than the peak voltage of the solar cell at the time of strobe light emission determined in advance (set to a voltage that reliably operates according to the detection speed). The presence or absence of snow on the surface can be detected. The snow cover is detected by operating the switch 3 to emit light from the strobe light emitting device 2. The switch 3 is operated by a timer (not shown) at an arbitrary time (when the output of the solar battery 5 is low after sunset or during the day). For example, it is preferable that the processing is automatically executed at an appropriate time interval (for example, every hour). When snow is detected, the snow determination circuit 21 outputs a snow detection signal (also simply referred to as a detection signal) 31.

FIG. 3 is a diagram of the snow determination circuit 21 inside the snow detection unit 1. 3 is a flip-flop circuit whose output is a detection signal 31. Reference numeral 11 denotes a detection start signal which indicates an output signal of a timer or the like, but may be a switch operated by a person. The timer 11 is a snow detection command circuit. Reference numeral 12 denotes a pulse generation circuit for generating a pulse signal for emitting a strobe light from the output of the switch circuit 3.
Reference numeral 13 denotes a delay circuit which is used to generate a signal D having a predetermined time length after the detection start signal A from the timer 11. 14
The comparison circuit compares the generated voltage of the solar cell 5 from the voltage divider 4 with a predetermined value (Vr in the figure), and outputs a signal E if the solar cell voltage is lower. Reference numeral 15 denotes a gate circuit which passes the output of the comparator 14 only during the signal D generated by the delay circuit 13 and sends it to the flip-flop circuit 10.

Next, the operation will be described. The timer 11 is turned on when the solar cell 5 is not generating power by receiving solar radiation, for example, at night or when there is snowfall, so that the signal A becomes L level. In response to the signal A, the output of the switch circuit 3 becomes H level, a strobe light emission signal is transmitted, and the strobe light emitting device 2 emits light. On the other hand, signal A
A signal D corresponding to the detection time Ts is generated by a signal B obtained by inverting the signal A and a signal C obtained by delaying the signal A, and the gate 15 is opened only while the signal D is at the H level. If snow is not generated on the light receiving surface of the solar cell 5, the voltage generated by the strobe light is input to the voltage divider 4 as the pulse voltage Vs.
If this voltage Vs is lower than the set voltage Vr, the comparator 14
The output E of the comparator 14 remains at the L level and remains unchanged. If the output E is high, the output E of the comparator 14 is inverted to the H level. This signal is input to the flip-flop 10 through the gate 15 to set the flip-flop 15. When the voltage is generated by sunlight, the voltage divider 4 also outputs, but if the timer 11 is not operating, the gate 15 is closed and the flip-flop 10 is not set.

During the detection time Ts (Ts is 5 to 10
When the output E becomes H level (preferably about 00 ms), the flip-flop 10 is set, it is determined that there is no snowfall, and it is held until the next detection. Note that, as described above, the detection operation performed at night may be performed at least once at sunrise, in the morning, before the time when the solar cell starts to generate power, and at a time that allows for the time required for snow melting. Alternatively, the detection may be performed at a set time by incorporating a clock in the snowfall detection unit 1, or at a time interval set by a timer or the like when the clock is not incorporated.

In the daytime, snow detection may be performed only when the solar cell 5 is not generating power. Therefore, the voltage of the solar cell 5 is constantly monitored by a voltage monitoring circuit (not shown) (not shown).
The generated voltage is a predetermined value (for example, several tens of% of the normal value in cloudy weather)
If the value below the value below continues for a long time, detection is started.
When the outside temperature is high, snow does not occur. Therefore, a temperature sensor (temperature detection circuit) not shown is provided, and the timer 11 is provided so that the snow detection is not performed if the temperature is higher than a certain level (for example, 3 degrees C). The circuit may be cut off to disable operation. This is called a snow detection command prohibition signal. Further, the strobe light emitting device 2 is installed outdoors so that light can be emitted to the light receiving surface of the solar cell 5, so that the strobe light emitting device 2 is stored in a storage box (not shown) that is not affected by rainfall and snow. A transparent light emitting surface such as glass is provided on the strobe light emitting side of the box. A heater may be built in the light emitting surface, and the heater may be turned on only a few hours before the time at which snow detection is performed and until the detection is completed.

Embodiment 2 FIG. FIG. 4 is a configuration diagram of an automatic snow melting device for a solar cell using the snow cover detection device of FIG. 1 described in the first embodiment for the solar cell. In the figure, reference numeral 7 denotes a power generation / snow melting mode changeover switch (hereinafter simply referred to as a switch), which is controlled by a snow detection signal 31 output from the snow detection unit 1. When snow cover is detected, the power generation / snow melting mode switch 7 is turned on, the inverter 8 is operated in the charging mode (converter mode), and power is supplied through the route of the power system 9 → the inverter 8 → the switch 7 → the solar cell 5. Alternatively, the solar cell 5 is energized using a DC power supply device or battery (not shown) to generate heat and melt snow. During snow melting, snow melting is temporarily suspended at appropriate time intervals (for example, 0.5 hours),
The snow check is performed again to prevent unnecessary power consumption, and if there is snow, the snow melting operation is continued.

The start of the timer 11 may be performed at a fixed time every day. However, in order to minimize the power generation failure of the solar cell 5 during the day due to snow, it is necessary to start the operation by the morning time when the solar cell starts generating power. Preferably, the snow melting operation has been completed. Therefore, solar cell power generation start time (varies according to season)
It is preferable to perform snow detection at a time that is earlier than the time required for snow melting (typically 2 to 3 hours depending on the supplied power). A sunrise time is known, and a timer that can set a seasonally changing time throughout the year is also known. It is obvious that the snow detection start time may be arbitrarily changed according to the presence or absence of a sunshine obstacle such as a building near the solar cell. The inverter 8 is a power supply that outputs a voltage according to the present invention. The power generation / snow melting mode changeover switch is the snow melting circuit according to the present invention.

Embodiment 3 FIG. In most cases, solar cells are not used alone, but are used directly in parallel with a plurality of cells. An array of solar cells for this purpose is called a solar cell array. In the case of a solar cell array, of course, it is not always necessary to provide all the solar cells with a snow detector. For a solar array,
Since the photovoltaic devices are installed at an angle, the solar cells arranged at the lower level than the upper level have more snow. In addition, snow does not always uniformly cover all solar cells, for example, depending on the wind direction. For this reason, the strobe light emitting device 2 of the first embodiment
And a plurality of switch circuits 3 for operating the same are installed in a portion of the solar cell array where snow is likely to increase, and the detection of snow is performed.

FIG. 5 shows a case where a solar cell 5a provided with a strobe light emitting device 2a and a solar cell 5b provided with a strobe light emitting device 2b are connected in parallel, and FIG. In any case, each of the switch circuits 3a, 3a is provided at an interval equal to or longer than the detection time Ts described in the first embodiment.
b is sequentially operated by a timer circuit (not shown), and the detection of FIG. 3 is performed.
The detection can be performed by one voltage divider 4 provided in the solar cell DC bus, and the snow determination circuit 21 in FIG. 3 does not need to be attached to each solar cell, and one circuit can be shared. In the case of the configuration of FIG. 5, the solar cells 5a, 5
b solar cell on / off switches 16a, 16b
By mounting only the solar battery open / close switch of the circuit in which snow was detected by the sequential detection of each of the above-described circuits, so that only the solar cell with snow is energized to melt snow.
Melt snow more efficiently.

[0028]

As described above, according to the present invention, the following effects can be obtained. 1. Since the snow itself on the light receiving surface of the solar cell is directly detected, there is little possibility of erroneous detection even when snow falls to the extent that snow does not exist. Further, the completion of snow melting can be detected.

2. It can be used at night, and can be used to detect snowmelt completion when snowmelt is completed during the night.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a snow detector for a solar cell according to a first embodiment.

FIG. 2 is an explanatory diagram of a voltage generated by a solar cell by strobe light.

FIG. 3 is a circuit diagram of a snow determination circuit of the snow detector of FIG. 1;

FIG. 4 is a configuration diagram of an automatic snow melting apparatus for a solar cell according to a second embodiment.

FIG. 5 is a snow detector for a solar cell according to the second embodiment;
It is a block diagram in case a solar cell is connected in parallel.

FIG. 6 shows a snow detector for a solar cell according to the second embodiment.
It is a block diagram in case a solar cell is connected in series.

FIG. 7 is a diagram illustrating general characteristics of a solar cell.

FIG. 8 is a configuration diagram of a conventional solar cell power generation system having a snowfall detection function and a snowmelt function.

[Explanation of symbols]

1 snow detection unit, 2 strobe light emitting device, 3 switch circuit, 4
Voltage divider (voltage detection means), 5 solar cells, 7 power generation /
Snow melting mode changeover switch (snow melting circuit), 8 inverter 11 timer (snow detection command circuit) 31 detection signal

Claims (9)

[Claims] 1. A solar cell having a light receiving surface for receiving sunlight, a strobe light emitting device installed to irradiate the light receiving surface, a switch circuit for operating the strobe light emitting device, and an output voltage of the solar cell Voltage detecting means for detecting the presence of snow on the light receiving surface of the solar cell by comparing the output voltage of the solar cell detected by the voltage detecting means at the time of light emission of the strobe light emitting device with a predetermined value. And a snow detection circuit for transmitting a snow detection signal. 2. The snow determination circuit according to claim 1, wherein the output voltage of the solar cell is compared with a predetermined value for a predetermined time Ts after the operation of the switch circuit. A snow detector for a solar cell. 3. A snow detection command for operating the switch circuit at an arbitrary cycle while the output voltage of the solar cell when the switch circuit according to claim 2 is not operated is equal to or lower than a predetermined value. An apparatus for detecting snow in a solar cell, comprising a circuit. 4. A snow detection device for a solar cell, comprising a snow detection command circuit for operating the switch circuit according to claim 2 at a predetermined time. 5. A temperature detecting circuit for detecting a temperature in the vicinity of a solar cell and transmitting a snow detection command prohibition signal to a snow detection command circuit when the temperature exceeds a predetermined value. The solar cell snow detection device according to claim 3. 6. The solar cell according to claim 1, wherein the strobe light emitting device includes a storage box having a glass window in which the strobe is stored, and a heater for heating the glass of the glass window. Snow detector. 7. A solar cell is a solar cell array including a plurality of solar cells, some of which have one strobe light emitting device. The solar cell array has one voltage detecting means, one snow determination. The apparatus for detecting snowfall of a solar cell according to claim 1, further comprising a circuit, and a timer circuit for sequentially operating the some strobe light emitting devices. 8. The predetermined time Ts according to claim 2 is 5 ms.
The snow detector for a solar cell according to claim 2, wherein the time is from 1000 ms to 1000 ms. 9. A snow detection device according to claim 1, further comprising a power supply device for outputting a voltage, wherein a voltage of the power supply device is changed for a predetermined time by a snow detection signal of the snow detection device.
An automatic snow-melting device for a solar cell, comprising a snow-melting circuit applied to the solar cell.